This invention relates generally to water filtration systems. Specifically, it relates to a faucet mounted water filter with a mechanism for notifying a user of the expiration of the useful life of the water filter media.
Faucet mounted water filtration systems are used in many households and other generally non-commercial environments for purifying drinking water. Such filters are known to eliminate several noxious substances, as well as to improve the taste, smell and appearance of tap water.
The filter media of conventional faucet mounted water filtration systems has a limited useful life. After a certain volume of water has passed through the media, the media becomes saturated with impurities and is unable to remove additional impurities from the water. However, with most conventional filters of this type, it is impossible for the user to accurately determine when the media is spent. Therefore, one of the problems associated with faucet mounted water filters has been the question of how a consumer knows when to change the filter media.
In some faucet mounted filtration systems, the practice has been to determine the life of the filter by the amount of time the filter is connected to a water supply, without regard to the volume of water which has actually passed through the filter. A manufacturer typically recommends that a filter be replaced after an amount of time reflective of the manufacturer's estimate of a typical user's filtered water needs. In many instances, the filter may become useless before the recommended time has elapsed because the flow through the filter was more than anticipated by the manufacturer. On the other hand, when water volume is less than anticipated, a filter may have additional useful life although the suggested filter lifetime has elapsed.
Several methods for measuring the life of water filters are known in the art. U.S. Pat. No. 4,885,081 to Oliver discloses a method of incorporating an electrical switch into the handle of a sink-mounted third faucet for a water filtration system installed below the sink or other remote location. The switch is connected to an electrical circuit which tallies the total elapsed time the handle is depressed to determine the amount of water processed. The disadvantages of U.S. Pat. No. 4,885,081 include the need for electronic circuitry disposed in a third faucet handle. For faucet mounted filtration systems, no third faucet is present. Also, each time the main faucet is used, water is not necessarily passing through the filter. Accordingly, the structure as described by Oliver is inapplicable.
A faucet mounted water filter with a timing mechanism has been proposed in U.S. pat. No. 4,431,533 to Wrede. This filter relies on the storage capacity of a battery to provide the timing mechanism for determining filter life. The battery life is chosen to correspond to filter life and a user is informed of the filter's expiration when a light on the filter no longer bums. This system has several disadvantages. As batteries have a limited shelf life, its possible that the battery will be partially discharged before the filtering system is connected to a faucet. Accordingly, the filter media will have remaining lifetime even though the battery is dead. Also, since the battery and indicator circuitry expires with the filter, the need for the circuitry to be disposable adds to the expense of the filter.
Thus, a first object of the present invention is to provide an improved faucet mounted water filtration system with an accurate indicator of the expiration of the filter media.
Another object of the present invention is to provide an improved water filtration system capable of accurately measuring the volume of water flow through the system.
It is a further object of the present invention to provide an improved filter life monitoring system that allows for the use of different filter medias with variable filter lives.
Yet another object of the present invention is to provide an improved filter life monitoring system of a compact and economical design consistent with a faucet mounted water filtration system.
Still another object of the present invention is to provide an improved water filtration system with reusable filter monitor circuitry and a disposable filter media.
These and other objects of the invention will be discussed or will be apparent from the following detailed description of the invention.